(1) Field of the invention
This invention relates to a method for reducing particles from an electrostatic chuck and an equipment for manufacturing a semiconductor, more particularly to a method for reducing particles from an electrostatic chuck and an equipment for manufacturing a semiconductor applying the method, which are usable for film-forming on a semiconductor wafer.
(2) Related Art Statement:
In each step of conveying a semiconductor wafer, exposure, film-forming by CVD, sputtering, etc., micro-processing, cleaning, etching, dicing, or the like, an electrostatic chuck is employed for absorbing and holding the semiconductor wafer.
Particularly, from the views of using, as an etching gas or a cleaning gas, a halogen-based corrosive gas such as ClF3, an equipment for manufacturing a semiconductor requires a high heat conduction for rapidly heating and cooling a semiconductor wafer with holding it and requires a high shock resistance so as not to be destroyed due to such a remarkable temperature change. Thus, a material made of dense aluminum nitride, dense alumina, or the like is promised.
On the other hand, inside the semiconductor-manufacturing equipment, the occurrence of particles, which results in defects of the semiconductor, is needed to be prevented. The particles are mainly generated from a backside surface of the semiconductor, a part of which attaches on the semiconductor wafer directly, the other part of which spreads in and attaches on a wall of a chamber. Then, the particles are peeled off of the wall, and thereby results in defects of a semiconductor.
In view of the above problems, JP A 7-245336 discloses a method in which uneven portions in an absorbing face of an electrostatic chuck made of ceramic material are ground by irradiating a plasma and the fine protuberances of the uneven portions are removed, and thereby the occurrence of particles is reduced. The method is based on the finding of the cause of particles"" occurrence that a silicon wafer having relatively low hardness is ground by the uneven portions when the silicon wafer contacts the uneven portions.
Moreover, JP A 8-55900 discloses a method in which a contacting shock of a silicon wafer with an electrostatic chuck is reduced by slowly rising a voltage to the electrostatic chuck when the silicon wafer is absorbed to the electrostatic chuck, and thereby the particles"" occurrence due to the uneven portions of the absorbing face in the electrostatic chuck is decreased.
The particles"" occurrence cannot be, however, sufficiently reduced by the above methods. That is, the semiconductor-manufacturing process requires that the number of particles within an 8-inch wafer, for example, is decreased to several hundreds, but the number can be decreased to only several thousand by the above methods.
Thus, even though the occurrence of the particles is reduced by the above methods, it is difficult to manufacture semiconductors with a sufficiently high yield.
It is an object of the present invention to provide a method for reducing particles from an electrostatic chuck, whereby occurrence of the particles is reduced in semiconductor-manufacturing processes and semiconductors can be manufactured with a sufficiently high yield, and an equipment for manufacturing semiconductors utilizing the method.
This invention relates to a method for reducing particles from an electrostatic chuck, wherein the difference between a wafer temperature before absorbing and a wafer maximum temperature after absorbing is 50xc2x0 C. or below when the wafer is absorbed onto the electrostatic chuck.
Particularly, from the views of using, as an etching gas or a cleaning gas, a halogen-based corrosive gas such as ClF3, an equipment for manufacturing a semiconductor requires a high heat conduction for rapidly heating and cooling a semiconductor wafer with holding it and requires a high shock resistance so as not to be destroyed due to such a remarkable temperature change. Thus, a material made of dense aluminum nitride, dense alumina, or the like is promised.
This invention still more relates to a semiconductor-manufacturing equipment, comprising a preheating means for preheating a wafer to a given temperature, a wafer""s preheating temperature-measuring means for measuring a preheating temperature of the preheated wafer, a preheating chamber having the preheating means and the wafer""s preheating temperature-measuring means, an electrostatic chuck for absorbing the wafer, a heating means for heat the wafer to a given film-forming temperature, a wafer""s heating temperature-measuring means for measuring a heating temperature of the wafer, and a film-forming chamber having the electrostatic chuck, the wafer""s heating temperature-measuring means and the heating means, said semiconductor-manufacturing equipment further comprising a controlling system which monitors and calculates electric signals from the wafer""s preheating temperature measured by the wafer""s preheating temperature-measuring means and the wafer""s heating temperature measured by the wafer""s heating temperature-measuring means, and, based on the calculated results, transmits controlling signals for controlling the preheating means and the heating means.
The reason for reduction of the particles"" occurrence, according to the present invention, is not clear, but can be considered as follows.
That is, it is considered that the difference between wafer""s heat expansions before and after absorbing can be reduced by making 50xc2x0 C. or below the difference between the wafer""s temperature before absorbing and the wafer""s maximum temperature after absorbing, and thereby the wafer is not often rubbed to an electrostatic chuck, so that an amount of the wafer to be ground is decreased.
Hereupon, the wording xe2x80x9cwafer""s temperature before absorbingxe2x80x9d means a temperature within 0 sec to 60 sec just before absorbing the wafer onto the electrostatic chuck.
On the other hand, the wording xe2x80x9cwafer""s maximum temperature after absorbingxe2x80x9d means a maximum temperature at which the wafer arrives in absorbing and releasing it onto and from the electrostatic chuck.